Study of the properties of polypropylene-PHB blends

Abstract

Polypropylene is ,with PVC and polyethylene, one of the most employed polymers for the production of daily life items. Although it is a thermoplastic polymer and nowadays the recycling conscience of the society is increasing, it is still found in urban wastes and therefore in landfills. Then, the main disadvantage is the permanence and the long life time of this type of plastics. The addition of biodegradable polymers has been claimed as a way to palliate this problem, since with degradation of the biodegradable fraction, the whole plastic object could collapse and practically be converted in a compostable stuff. For example, in the report published by NOLAN-ITU Pty Ltd on October 2002, there is a full revision about biodegradable polymers. It is worth mentioning starch based polymers as well as biodegradable polyesters. In the biodegradable polyesters family, it is possible to find polyhydroxyalkanoates, which are produced naturally by different kind of bacteria. The most common polyhydroxyalkaonates are based on poly 3-hydroxybutyrate (PHB) and its copolymers with 3-hydroxy-n-valeric acid (PHBV). Concentrations reported in bibliography for PHB with oxidized polypropylene lie up to 10% , higher PHB concentrations may involve an adverse effect on mechanical properties of such blends, although the highest PHB concentrations, the most biodegradable blend is obtained. In the case of more polar polymers, as PVC, higher PHB concentrations (up to 70%) have been reported. Thus, miscibility of polyhydroxyalcanoates and its effect on mechanical properties is one of the factors to have in mind. On the other hand, SEBS copolymers have also been used as a impact modifier for polypropylene, while in some other cases, they have been used as compatibilizers between polymers of different polarities. The aim of the present work has been the study of the properties of ternary blends PP-PHB-SEBS, where polypropylene is the major component.